CVE-2026-3802 is a stack-based buffer overflow vulnerability identified in the Tenda i3 router firmware version 1.0.0.6(2204). The vulnerability resides in the formexeCommand function, specifically in the handling of the cmdinput parameter passed to the /goform/exeCommand endpoint. Due to insufficient bounds checking, an attacker can craft a specially malformed cmdinput argument that causes a stack overflow, potentially overwriting the return address or other critical stack data. This flaw enables remote code execution without requiring authentication or user interaction, as the vulnerable endpoint is accessible remotely over the network. The vulnerability's CVSS 4.0 vector (AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:P) indicates network attack vector, low complexity, no authentication, and partial exploit code availability. Successful exploitation can lead to full compromise of the device, allowing attackers to execute arbitrary commands, disrupt device operation, or pivot into internal networks. The vulnerability affects a widely deployed consumer and small business router model, increasing the potential attack surface. Although no active exploits have been reported in the wild, the public disclosure of exploit code raises the likelihood of imminent attacks. No official patches have been linked yet, emphasizing the need for immediate mitigation steps.

The impact of CVE-2026-3802 is significant for organizations and individuals relying on Tenda i3 routers. Exploitation can lead to remote code execution, enabling attackers to take full control of the device. This compromises confidentiality by allowing interception or manipulation of network traffic, integrity by enabling unauthorized configuration changes or malware installation, and availability by causing device crashes or denial of service. Attackers can leverage compromised routers as footholds for lateral movement into internal networks, potentially accessing sensitive systems and data. The vulnerability's remote and unauthenticated nature increases the risk of widespread exploitation, especially in environments where these routers are exposed to the internet. Small businesses and home users with limited security monitoring are particularly vulnerable. The lack of known exploits in the wild currently limits immediate impact but the public exploit disclosure may lead to rapid weaponization. Overall, this vulnerability poses a critical threat to network security and operational continuity.

To mitigate CVE-2026-3802, organizations should first verify if they are using the affected Tenda i3 firmware version 1.0.0.6(2204). Since no official patches are currently linked, immediate steps include disabling remote management interfaces to prevent external access to the /goform/exeCommand endpoint. Network segmentation should be enforced to isolate vulnerable devices from critical infrastructure. Employ firewall rules to restrict inbound traffic to trusted sources only. Monitoring network traffic for unusual requests targeting the /goform/exeCommand path can help detect exploitation attempts. Consider replacing affected devices with models from vendors providing timely security updates if patching is delayed. Additionally, vendors and users should subscribe to Tenda security advisories for updates. Applying intrusion detection/prevention systems (IDS/IPS) signatures targeting this vulnerability can provide additional protection. Finally, educating users about the risks of exposing router management interfaces to the internet is essential to reduce attack surface.